Simplified doppler antenna system

ABSTRACT

Disclosed is a simplified antenna system for radiating a frequency coded pattern using a beam-port antenna. The antenna system radiates a pattern wherein the frequency of the radiated wave energy varies over a selected portion of the region of space within which the antenna radiates and wherein the frequency of the radiated signal within the remaining portion or portions of the region is representative of the sense of angular displacement from the selected portion. The antenna system includes a multiple-beam antenna unit and means for supplying the ports of the antenna unit corresponding to antenna beams in the selected portion with wave energy signals having varying relative phase. The ports of the antenna unit corresponding to antenna beams in the remaining portion of the regions of space are supplied with wave energy signals having the same phase as the wave energy signals supplied to the port corresponding to the antenna beam within the selected portion which is adjacent to the remaining portion.

United States Patent [191 Litt et al.

[ Oct. 21, 1975 r SIMPLIFIED DOPPLER ANTENNA SYSTEM [75] Inventors: Stuart P. Litt, Greenlawn; Melvin J. Zeltser, Oceanside; Richard J. Giannini, Setauket; Richard F. Frazita, Deer Park, all of NY.

[73] Assignee: Hazeltine Corporation, Greenlawn,

[22] Filed: Nov. 5, 1974 [21] Appl. No.: 521,118

[52] US. Cl. 343/106 D; 343/100 SA; 343/113 DE; 343/754; 343/854 [51] Int. Cl. GOlS 1/38; HOlQ 3/26 [58] Field of Search... 343/100 SA, 106 D, 113 DE, 343/840, 854, 754

[56] References Cited UNITED STATES PATENTS 3,864,679 2/1975 Hannan et al. 343/854 Primary ExaminerEli Lieberman 20 22c 22d 22e 24b I6i [57] ABSTRACT Disclosed is a simplified antenna system for radiating a frequency coded pattern using a beam-port antenna. The antenna system radiates a pattern wherein the frequency of the radiated wave energy varies over a selected portion of the region of space within which the antenna radiates and wherein the frequency of the radiated signal within the remaining portion or portions of the region is representative of the sense of angular displacement from the selected portion. The antenna system includes a multiple-beam antenna unit and means for supplying the ports of the antenna unit corresponding to antenna beams in the selected portion with wave energy signals having varying relative phase. The ports of the antenna unit corresponding to antenna beams in the remaining portion of the regions of space are supplied with wave energy signals having the same phase as the wave energy signals supplied to the port corresponding to the antenna beam within the selected portion which is adjacent to the remaining portion.

13 Claims, 11 Drawing Figures US. Patent Oct. 21, 1975 Sheet10f3 3,914,765

20 22c 22d 22e 24b |6i FIG.

FIG. 2

US. Patent Oct.21, 1975 Sheet20f3 3,914,765

AMPLITUDE AMPLITUDE FIG. 3B

FREQUENCY FIG. 3C

ANGLE FIG. 3

US. Patent Oct.21, 1975 Sheet3 0f3 3,914,765

FIG. 4E PHASE FIG. 40 0 FIG. 40 o FIG. 4B 0 I I I I FIG 4A 0 1'0 TIME+ FIG. 4

(2;) STATE "I" (g STATE "0" FIG. 5

, I 1 SIMPLIFIED DOPPLER ANTENNA SYSTEM BACKGROUND or THE INVENTION This invention relates to antenna systems for radiating a doppler coded pattern and in particular to such systems which radiate a doppler coded pattern using a multiple beam antenna such as described in the copending allowed application of Hannan, et al., Ser. No. 347,506, filed Apr. 3, 1973, now US. Pat. No. 3,864,679, which is assigned to the same assignee as the present application.

The above-referenced copending application discloses a novel antenna system for radiating a doppler coded pattern using a multiple-beam antenna. A doppler coded pattern is one in which the frequency of the radiated wave energy varies with one of the components of angular displacement from the antenna. A multiple-beam antenna, or beam-port antenna, is an antenna capable of radiating a plurality of antenna beams in different directions from a common aperture and having a number of wave energy input ports, equal to the number of antenna beams, such that wave energy supplied to one of the ports is radiated in a corresponding one of the beams. The antenna system disclosed in the above-referenced application includes means for simultaneously supplying each of the ports of a beamport antenna with wave energy signals during a time period. The phase of the wave energy signals supplied to each port, measured with respect to the phase of the signals supplied to the antenna port corresponding to an adjacent antenna beam, varies during the time period between a predetermined pair of values. The resulting radiation pattern had a frequency which varied with a component of angular'displacement from the antenna within a desired region of space.

The antenna system disclosed in the copending application is usable in a doppler microwave landing system wherein it is necessary that all portions of the region of space within which the antenna radiates be accurately encoded with a radiation frequency which is representative of a component of angular direction from the antenna system. This requirement is appropriate for a microwave landing system installation at a large air terminal facility wherein, because of a heavy volume of air traffic, it is necessary to use multiple approaches to guide aircraft to landings. In air terminals having less severe traffic requirements, a single instrument approach or glide slopefmay be adequate to handle the expected volume of air traffic. In such an installation it is only necessary toaccurately encode a selected portion of the region of space within which the antenna radiates, that is theportion corresponding to the angular regions close to the selected glide slope, and the remaining portions of the region may be encoded with a radiated frequency which is representative only of the sense of angular displacement from the selected portion containing the glide slope. Such a simplified system would provide a pilot with accurate angular information when he is in the selected portion of the region of space around the glide slope, and with mere corrective information, for example, fly up or fly down when he is below or above, respectively, the selected portion of the region of space.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an antenna system for radiating a frequency coded pattern utilizing a multiple-beam antenna.

It is a further object of the present invention to provide such an antenna system wherein the frequency of the radiated signal varies with a component of angular direction within a selected portion of the region of space within which the antenna radiates, and wherein the frequency of the radiated signal is representative of the sense of angular displacement from the selected portion within the remaining portion or portions of the region of space.

It is a still further object of the present invention to provide such an antenna system having simplified construction.

In accordance with the present invention there is provided an antenna system for radiating wave energy into a desired region of space during a selected time period in a desired radiation pattern, wherein the frequency of the radiated wave energy within a selected portion of the region varies with at least one of the components of angular direction from the antenna system and wherein the frequency of the radiated wave energy within at least one remaining portion of the region is representative of the sense of the component of angular displacement with respect to the selected portion of the region. The antenna system includes an antenna unit capable of radiating a plurality of beams in different directions within the selected region of space from a common aperture. The antenna unit has a plurality of wave energy input ports such that each of the ports corresponds to one of the beams. The antenna system further includes means for simultaneously supplying a plurality of wave energy signals during the time period, one to each of the ports. Each wave energy signal supplied to a port corresponding to a beam primarily within the selected portion has a phase, measured with respect to the phase of the wave energy signal supplied to the port corresponding to an adjacent antenna beam, which vvaries during the time period between a predetermined pair of values, the variation being less than 360 and the sense of the variation being alike for pairs ofantenna ports corresponding to similarly adjacent beams. Each wave energy signal supplied to a port corresponding to a beam within the remaining portion has the same phase as the wave energy signal supplied to the port corresponding to the antenna beam within the selected portion which is adjacent to the remaining portion. When the signals are supplied to the antenna ports, the antenna radiates the desired radiation pattern.

For a better understanding of the present invention,

together with other and further objects thereof, reference is-had to the following description, taken in conjunction with the accompanying drawings, and its .scope will be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 3A-3C show the radiation characteristics of the FIG. 1 antenna system.

FIGS. 4A4E illustrate the phase variation of the wave energy signals used in the FIG. 1 embodiment.

FIG. 5 illustrates a variation of the signal supplying circuit for the system illustrated in FIG. 2.

DESCRIPTION AND OPERATION OF THE EMBODIMENT OF FIG. 1

FIG. 1 is a partially perspective, partially schematic illustration of an antenna system constructed in accordance with the present invention. The antenna system includes an antenna unit, which comprises means for focusing incident wave energy, in this case reflector 12, and means for illuminating the focusing means, namely antenna feeds 14. The antenna unit will radiate wave energy into a selected region of space in response to wave energy signals supplied to ports 16 associated with feeds 14. The particular antenna unit illustrated in FIG. 1 is built in accordance with the invention of P. W. I-Iannan described in copending allowed application Ser. No. 347,505, filed Apr. 3, 1973, now U.S. Pat. No. 3,881,178, entitled Antenna System for Radiating Multiple Planar Beams", which is assigned to the same asignee as the present application.

Antenna feeds 14d, 142 and l4fhave their respective input ports 16d, l6e and 16f connected to individual phase shifter 22b, 22c and 22d respectively. Antenna feeds 14a, 14b and 14c are all connected via their respective input ports 16a, 16b and 160 to a common phase shifter 22a by power divider 24a. Likewise feeds 14g, 14h and 141' are all connected via their respective input ports 16g, 16h and 161' to a common phase shifter 22e. Wave energy signals are supplied to phase shifters 22 from oscillator 18 via power divider 20. Control unit 26 is provided for controlling the operation of phase shifters 22 in a manner described hereinafter.

The arrangement of components in antenna system 10 is similar to that described in the above-mentioned copending application of l-Iannan, et al., Ser. No. 347,506, except that in the system described in the copending application a separate phase shifter is provided for each of the feed elements. The present invention provides a simplification and cost advantage over the system described in the copending application since fewer phase shifters are required for a system using the same number of antenna feeds. This saving is evident from the embodiment of FIG. 1 wherein feeds 14a, 14b and 140 all share the output of phase shifter 22a and feeds 14g, 14h and 141' all share the output of phase shifter 22e. The trade-off for the reduced complexity of the present invention is a reduction in system capability which is acceptable in many applications. In particular the present invention provides frequency coding of angular direction from the antenna over only a selected portion of the region of space into which it radiates and provides a radiation frequency representative of the sense, but not amplitude of deviation from the selected portion in the remaining portions of the region.

The antenna unit of the FIG. 1 embodiment is of a type which may be classified as a beam-port antenna. This type of antenna is capable of radiating a plurality of antenna beams in different directions within a region of space from a common aperture. A beam-port antenna has a plurality of wave energy input ports such that wave energy supplied to one of the ports is radiated in a corresponding one of the beams. In the FIG.

l antenna unit, each. of the feeds 14 illuminates reflector 12 with a wave energy pattern in response to wave energy signals supplied to a corresponding one of the input ports 16. Reflector 12 radiates an antenna beam 5 in a different direction in space in response to the wave 1 energy pattern from each of the feeds 14. The operation of this type of antenna and the nature of the planar beams associated with the configuration of FIG. 1 are more fully described in copending allowed application Ser. No. 347,505, referenced above. As will become evident to those skilled in the art, other types of beamport antennas may also be used in antenna systems constructed in accordance with the present invention.

FIG. 3 illustrates the desired radiation pattern for the embodiment of FIG. 1. FIG. 3A illustrates the individual antenna beams (a) through (i) which would be radiated by the FIG. 1 antenna unit in response to wave energy signals supplied to input ports 16a through 161, respectively. The antenna beams are illustrated as a function of radiation angle as measured in a plane perpendicular to the focal axis of reflector 12. When wave energy signals are simultaneously supplied to all of the input ports 16a through 161' with a phase relation which does not cause interference of the respective antenna beams in space it is possible to achieve a composite radiation pattern with a desired amplitude versus angle characteristic as illustrated in FIG. 3B. The composite pattern illustrated in FIG. 3B has a relatively constant amplitude over the desired region of space and has a sharp cutoff of radiation at the edges of the region corresponding to the radiation slope of the narrow component antenna beams illustrated in FIG. 3A. Those skilled in the art will recognize that the composite radiation pattern illustrated in FIG. 38 can be made to have I other than constant amplitude and may be adjusted to have any desired amplitude pattern by altering the amplitude of the wave energy supplied to the antenna ports 16 corresponding to the component antenna beams illustrated in FIG. 3A.

FIG. 3C illustrates the frequency of the radiation pattern produced by the antenna unit of FIG. 1 in accordance with'the present invention. The region of space into which the antenna system radiates has been subdivided into three portions, indicated as I, II and III in FIG. 3. Portion I is a selected region wherein the frequency of the radiated wave energy varies as a function of the radiation angle. A part of portion I, designated IA in FIG. 3C, is a region surrounding a desired angle 6 wherein the variation of radiation frequency is linear with radiation angle. If the FIG. 1 antenna system is utilized as a guidance antenna in a doppler microwave landing system, the desired angle 0 would be the landing glide slope and, because of the linear variation of radiated frequency within part IA of the radiation region, very accurate angle guidance may be obtained at angles close to the desired angle. In the remaining parts of selected portion I, the frequency of radiation varies in a non-linear manner and it is either more difficult to obtainaccurate angle information or the information obtained is less accurate. The remaining portions II and III of the region have substantially constant radiated frequency. Within these portions an indication of angle with respect to the antenna system is not desired, only the sense of deviation from the glide slope angle 0 or desired portion I is necessary. Thus, if the antenna systern of FIG. 1 is used in a microwave landing system as an elevation guidance antenna, an aircraft within angular portions [I and III could determine whether it was flying above or below the desired glide slope until it en-' tered the region I and could then determine the actua angular deviation from the glide slope.

-The desired radiation pattern of FIG.3 is achieved by simultaneously supplying wave energy signals to antenna ports 16 with a selected phase during a selected time period. Illustrated in FIG. 4 is the phase of the wave energy supplied to the ports of the FIG. 1 antenna during a succession of such time periods T1, T2, T3 and T4. As may be seen from FIG. 3A, antenna ports 16c, 16d, 16e, 16f and 16g correspond to antenna beams within the selected portion I of the region of space wherein the frequency of the radiated wave energy varies as a function of angle from the antenna. The phase of the wave energy signal supplied to each of these antenna ports, measured with respect to the phase of the wave energy signal supplied to the antenna port corresponding to an adjacent antenna beam, varies during each time period between a predetermined pair of values. In the illustration of FIG. 4, the phase indicated by the FIG. 4A diagram is taken as the reference phase for all ofthe phase values indicated in FIGS. 48 through 4E,'but it will be recognized that the phase indicated in each of the remaining phase diagrams varies with respect to that of the adjacent diagrams in FIG. 4. The phase represented in FIG. 4A is the phase of wave energy signals supplied to antenna port 16c by phase shifter 22a, likewise the phase of FIGS. 4B, 4C, 4D and 4E are supplied to antenna ports 16d, 16e, 16f and 16g by phase shifters 22b, 22c, 22d and 222, respectively. In the illustration, each of the respective phase values varies with respect to the adjacent phase value linearly and between like pairs of predetermined values. For example, if phase 43 varies from 45 to +45 with respectto phase 4A, then phase 4C varies from 90 to +90 with respect to phase 4A, or from 45 to +45 with respect to phase 48. This variation is the same as that described in copending application Ser. No. 347,506. 1

The effect of the linear phase variation illustrated in FIG. 4 is to cause each wave energy signal to have effectively a different frequency during each of the time intervals. As a result each radiated beam has a different frequency and the desired frequency variation within portion I of the region of radiation is achieved since each beam within that portion has a slightly different frequency. As is pointed out in the copending application, Ser. No. 347,506, the phase variation must be limited to a specific duration in time, because if allowed to continue indefinitely adjacent antenna beams would become out of phase and there would be cancellation in the radiated pattern. To avoid cancellation the variation in phase between ports corresponding to adjacent antenna beams must be less than 360 and is usually much less. In the illustration of FIG. 4 the antenna ports 16 are chosen to have phase locations along their respective transmission lines which correspond to equal phase of the radiated patterns. Thus, if equalv phase signals are supplied to adjacent antenna ports 16 the corresponding antenna beams will be in phase. It may be seen in FIG. 4 that during each time period there is a time, to, when all of the wave energy signals have equal phase. Thus at this time all of the antenna beams are in phase and if the variation of phase between wave energy signals is considerably less than i180, the adjacent radiated beams will not cancel each other. It will be recognized that the phase actually used for each of the wave energy signals must be adjusted to account for the actual phase location of the respective antenna ports 16 with respect to the radiated antenna beams.

As shown in FIG. 1, phase shifter 22a supplies wave energy signals via power divider 24a to ports 16a and 16b as well as port 16c. Ports 16a and 16b correspond to antenna beams within one of the remaining portions of the region of space, in particular portion III. Since the antenna ports 16a and 16b are supplied with wave energy signals having the same phase variation as the signals supplied to port 16c, the radiated antenna pattern in portion III does not have any significant frequency variation with radiation angle and has substantially the frequency associated with the direction of the antenna beam corresponding to port l6c. ln a doppler microwave landing system this frequency is representative of the sense of angular deviation from the selected portion I, but because there is substantially no variation of frequency with radiation angle, there is no available measure of the magnitude of angular deviation.

Likewise wave energy signals are supplied to antenna ports 16h and l6i with the same phase variation as the signals supplied to port 16g. Consequently there is no substantial variation of the frequency of radiation in portion II of the region but the radiated frequency can be used -to determine the sense of deviation from selected portion I.

The operation of the FIG. 1 system and its advantages over the system described in copending application Ser. No. 347,506 will now become apparent. Wave energy signals from oscillator 18 are supplied to phase shifters 22 by power divider 20. Control unit 26 causes operation of phase shifters 22 so that the phase of the wave energy signals supplied to antenna ports 16 have a phase variation similar to that shown in FIG. 4. Phase shifters 22 can be any type suitable for operation at the radiation frequency of the antenna. Typical of each phase shifters are ferrite phase shifters and diode phase shifters whose properties are well known to those skilled in the art. Control unit 26 would typically be designed out of digital logic elements or other electronic circuits to provide the appropriate driving signals to operate phase shifters 22 so that the wave energy signals supplied to antenna ports 16 have the required phase variation as illustrated in FIG. 4. Power dividers 24a and 24b are provided so that the phase of wave energy signals for ports 16a, 16b and 16c may be controlled by a single phase shifter 22a and the phase of wave energy signals for ports 16g, 16h and l6i may be controlled by a single phase shifter 22 e. The advantage of the present invention is therefore a reduction in the number of phase shifters required as compared to a system for radiating in a comparable angular region in accordance with the invention of the copending application. Those skilled in the art will recognize that the relative distribution of the amplitude of the radiated signal within the region of space may be selected by appropriate selection of power dividers 20, 24a and 24b, which regulate the amount of energy supplied to each of ports 16. It will also be evident to those skilled in the art that the components of antenna system 10, particularly phase shifters 22 and power dividers 24 may be re-arranged to change the respective angular locations of the selected portion I and remaining portions II and III of the angular region of space.

DESCRIPTION OF THE EMBODIMENTS OF FIG. 2

FIG. 2 illustates an alternate embodiment of the present invention wherein the antenna unit comprises a pill-box" antenna 28. The signal supplying components of the system of FIG. 2 are substantially the same as used in the FIG. 1 system, except there is provided only a single power divider 24. Consequently there is only one remaining portion of the region of space into which the antenna system radiates wherein the radiation frequency is representative of the sense of angular deviation from the selected portion. An antenna system of this type would be useful in a landing system wherein the desired glide slope is at a relative low elevation angle or a relatively high elevation angle and therefore at one end of the angular region of space into which the antenna radiates.

Pill-box antenna 28 comprises a group of feed elements 14 which may be dipoles or radiating probes enclosed between conductive metal plates 30 and 32. There is also provided dielectric lens 34 for focusing wave energy radiated from feed elements 14. The particular antenna of FIG. 2 has the shape of a sectoral horn and radiates a beam in a unique direction from the horn opening in response to wave energy supplied to each of feed elements 14 via ports 16. It will therefore be recognized that antenna 28 is a beam-port antenna within the requirements of the present invention. The radiation from antenna 28 is in the form of conical beams as opposed to the planar beams which will be radiated by the antenna unit of FIG. 1. Consequently the resulting frequency coding in accordance with the present invention will be with respect to a component of angular direction measured in a conical coordinate system, whereas the FIG. 1 antenna will radiate signals which are frequency coded in planar coordinates.

FIG. 5 illustrates an alternative embodiment of the signal supplying means used in the antenna system of FIG. 2. The FIG. 5 embodiment includes transfer switches 36a, 36b and 360 disposed between antenna ports 16 and the phase shifter 22. Also illustrated is the switching characteristics for transfer switches 36. When switches 36 are in the 0" position power divider 24 is connected to ports 16d, 16e, l6fand 16g as illustrated in FIG. 2 and phase shifters 22a, 22b and 22c are connected to ports 16a, 16b and 160 respectively. In this configuration the selected portion of the region of space includes that into which the beams associated with ports 16a, 16b, I60 and 16d radiate. When switches 36 are in the 1" position phase shifters 22a, 22b and 220 are connected to ports 16e, 16f and 16g respectively and power divider 24 is connected to ports 16 a, 1611, 16c and 16d. By a suitable adjustment in the phase commands supplied to phase shifters 22, the antenna may operate with the selected portion of the region of space corresponding to the direction of the antenna beams associated with antenna ports 16d, 16e, 16f and 16g. Thus by including switches 36, the selected portion may be moved to a different angular part of the region.

While the invention has been described and is claimed with reference to transmitting systems, those skilled in the art will recognize that such systems are reciprocal and the invention may also be applied to receiving systems; it is therefore intended that the appended claims shall apply to both transmitting and receiving systems.

While there have been described what are believed to be preferred embodiments of the present inventions, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An antenna system for radiating wave energy into a desired region of space during a selected time period in a desired radiation pattern, wherein the frequency of said radiated wave energy within a selected portion of said region varies with at least one of the components of angular direction from said antenna system and wherein the frequency of said radiated wave energy within at least one remaining portion of said region is representative of the sense of said component of angular displacement with respect to said selected portion of said region, comprising:

an antenna unit capable of radiating a plurality of beams in different directions within said region of space from a common aperture, and having a plurality of wave energy input ports such that each of said ports corresponds to one of said beams;

and means for simultaneously supplying a plurality of wave energy signals during said time period, one to each of said ports, each wave energy signal supplied to a port corresponding to a beam primarily within said selected portion having a phase, measured with respect to the phase of the wave energy signal supplied to the port corresponding to an adjacent antenna beam, which varies during said time period between a predetermined pair of values, said variation being less than 360, and the sense of said variation being alike for pairs of antenna ports corresponding to similarly adjacent beams, and each wave energy signal supplied to a port corresponding to a beam primarily within said remaining portion having the same phase variation as the wave energy signal supplied to the port corresponding to the antenna beam within said selected portion which is adjacent to said remaining portion;

whereby when said signals are supplied to said antenna ports said antenna radiates said desired radiation pattern.

2. An antenna system for radiating wave energy into a desired region of space duringa selected time period in a desired radiation pattern, wherein the frequency of said radiated wave energy within a selected portion of said region varies with at least one of the components of angular direction from said antenna system, and wherein the frequency of said radiated wave energy within at least one remaining portion of said region is representative of the sense of said component of angular displacement with respect to said selected portion of said region, comprising:

an antenna unit capable of radiating a plurality of beams in different directions within said region of space from a common aperture, and having a plurality of wave energy input ports such that each of said ports corresponds to one of said beams; means for controlling the phase of wave energy supplied to the ports of said antenna unit such that each wave energy signal supplied to a port corresponding to a beam primarily within said selected portion has a phase, measured with respect to the phase of the wave energy signal supplied to the port corresponding to an adjacent antenna beam, which varies during said time period between a predetermined pair of values, said variation being less than 360, and the sense of said variation being alike for pairs of antenna ports corresponding to similarily adjacent beams, and such that each wave energy signal supplied to a port corresponding to a beam within said remaining portion has the same phase variation as the wave energy signal supplied to the port corresponding to the antenna beam within said selected portion which is adjacent to said remaining portion;

and means for simultaneously supplying wave energy signals during said time period to said antenna ports via said phase control means;

whereby when said signals are supplied to said antenna ports said antenna radiates said desired radiation pattern.

3. An antenna system as specified in claim 2 wherein there are two remaining portions of said region, oppositely disposed with respect to said selected portion of said region and wherein said wave energy signals supplied to said ports corresponding to beams within each of said remaining portions have the same phase as the wave energy signal supplied to the port corresponding to the antenna beam within said selected portion which is adjacent to the corresponding remaining portion.

4. An antenna system as specified in claim 2 wherein each of said wave energy signals supplied to a port corresponding to said selected portion is controlled to have a phase which varies linearly with time between said predetermined pair of values.

5. An antenna system as specified in claim 2 wherein the frequency of said radiated wave energy within part of said selected portion of said region varies linearly with said component of angular direction from said antenna system and wherein said predetermined pair of phase values is alike for all antenna ports corresponding to beams within said selected region.

6. An antenna system as specified in claim 2 wherein said means for controlling the phase of wave energy signals comprises a plurality of phase shifters and a control unit for controlling the operation of said phase shifters.

7. An antenna system as specified in claim 6 wherein said means for supplying wave energy signals comprises:

a source of wave energy signals;

a first power divider for supplying said signals to said phase shifters;

a second power divider for supplying signals from a selected one of said phase shifters to the antenna ports corresponding to antenna beams in said remaining portion and to said antenna port corresponding to the antenna beam in said selected portion which is adjacent to said remaining portion;

and transmission lines for interconnecting said source of wave energy signals, said first and second power dividers, said phase shifters and said antenna ports.

8. An antenna system as specified in claim 2 which additionally includes means for switching disposed between said means for supplying wave energy signals and said input ports whereby said selected portion may be chosen to have different angular locations within said desired region.

9. An antenna system as specified in claim 2 wherein said antenna unit comprises means for focusing incident wave energy and a plurality of feed elements, each having a wave energy input port, for illuminating said focusing means with wave energy patterns, such that each of said feed elements corresponds to one of said beams.

10. An antenna system as specified in claim 9 wherein the frequency of said radiated wave energy within a part of said selected portion varies substantially linearly with said component of angular direction from said antenna system, wherein said feed elements are displaced from each other by a substantially equal amount and wherein said predetermined pair of values is alike for all pairs of ports corresponding to similarly adjacent beams within said selected portion of said region.

'11. An antenna system as specified in claim 9 wherein said means for focusing incident wave energy comprises a cylindrical reflector.

12. An antenna system as specified in claim 9 wherein said means for focusing incident wave energy comprises a focusing lens located between a pair of parallel conductive plates and wherein said feed elements comprise feed elements located between said pair of parallel plates.

13. An antenna system as specified in claim 9 wherein the wave energy signals supplied to each of said ports have substantially equal amplitude thereby causing said antenna to radiate substantially equal amounts of radiation energy over said selected region of space and radiate smaller amounts of radiation energy in the remaining regions of space. 

1. An antenna system for radiating wave energy into a desired region of space during a selected time period in a desired radiation pattern, wherein the frequency of said radiated wave energy within a selected portion of said region varies with at least one of the components of angular direction from said antenna system and wherein the frequency of said radiated wave energy within at least one remaining portion of said region is representative of the sense of said component of angular displacement with respect to said selected portion of said region, comprising: an antenna unit capable of radiating a plurality of beams in different directions within said region of space from a common aperture, and having a plurality of wave energy input ports such that each of said ports corresponds to one of said beams; and means for simultaneously supplying a plurality of wave energy signals during said time period, one to each of said ports, each wave eneRgy signal supplied to a port corresponding to a beam primarily within said selected portion having a phase, measured with respect to the phase of the wave energy signal supplied to the port corresponding to an adjacent antenna beam, which varies during said time period between a predetermined pair of values, said variation being less than 360*, and the sense of said variation being alike for pairs of antenna ports corresponding to similarly adjacent beams, and each wave energy signal supplied to a port corresponding to a beam primarily within said remaining portion having the same phase variation as the wave energy signal supplied to the port corresponding to the antenna beam within said selected portion which is adjacent to said remaining portion; whereby when said signals are supplied to said antenna ports said antenna radiates said desired radiation pattern.
 2. An antenna system for radiating wave energy into a desired region of space during a selected time period in a desired radiation pattern, wherein the frequency of said radiated wave energy within a selected portion of said region varies with at least one of the components of angular direction from said antenna system, and wherein the frequency of said radiated wave energy within at least one remaining portion of said region is representative of the sense of said component of angular displacement with respect to said selected portion of said region, comprising: an antenna unit capable of radiating a plurality of beams in different directions within said region of space from a common aperture, and having a plurality of wave energy input ports such that each of said ports corresponds to one of said beams; means for controlling the phase of wave energy supplied to the ports of said antenna unit such that each wave energy signal supplied to a port corresponding to a beam primarily within said selected portion has a phase, measured with respect to the phase of the wave energy signal supplied to the port corresponding to an adjacent antenna beam, which varies during said time period between a predetermined pair of values, said variation being less than 360*, and the sense of said variation being alike for pairs of antenna ports corresponding to similarily adjacent beams, and such that each wave energy signal supplied to a port corresponding to a beam within said remaining portion has the same phase variation as the wave energy signal supplied to the port corresponding to the antenna beam within said selected portion which is adjacent to said remaining portion; and means for simultaneously supplying wave energy signals during said time period to said antenna ports via said phase control means; whereby when said signals are supplied to said antenna ports said antenna radiates said desired radiation pattern.
 3. An antenna system as specified in claim 2 wherein there are two remaining portions of said region, oppositely disposed with respect to said selected portion of said region and wherein said wave energy signals supplied to said ports corresponding to beams within each of said remaining portions have the same phase as the wave energy signal supplied to the port corresponding to the antenna beam within said selected portion which is adjacent to the corresponding remaining portion.
 4. An antenna system as specified in claim 2 wherein each of said wave energy signals supplied to a port corresponding to said selected portion is controlled to have a phase which varies linearly with time between said predetermined pair of values.
 5. An antenna system as specified in claim 2 wherein the frequency of said radiated wave energy within part of said selected portion of said region varies linearly with said component of angular direction from said antenna system and wherein said predetermined pair of phase values is alike for all antenna ports corresponding to beams within said selected region.
 6. An antenna system as specified in claim 2 wherein said means for controlling the phase of wave energy signals comprises a plurality of phase shifters and a control unit for controlling the operation of said phase shifters.
 7. An antenna system as specified in claim 6 wherein said means for supplying wave energy signals comprises: a source of wave energy signals; a first power divider for supplying said signals to said phase shifters; a second power divider for supplying signals from a selected one of said phase shifters to the antenna ports corresponding to antenna beams in said remaining portion and to said antenna port corresponding to the antenna beam in said selected portion which is adjacent to said remaining portion; and transmission lines for interconnecting said source of wave energy signals, said first and second power dividers, said phase shifters and said antenna ports.
 8. An antenna system as specified in claim 2 which additionally includes means for switching disposed between said means for supplying wave energy signals and said input ports whereby said selected portion may be chosen to have different angular locations within said desired region.
 9. An antenna system as specified in claim 2 wherein said antenna unit comprises means for focusing incident wave energy and a plurality of feed elements, each having a wave energy input port, for illuminating said focusing means with wave energy patterns, such that each of said feed elements corresponds to one of said beams.
 10. An antenna system as specified in claim 9 wherein the frequency of said radiated wave energy within a part of said selected portion varies substantially linearly with said component of angular direction from said antenna system, wherein said feed elements are displaced from each other by a substantially equal amount and wherein said predetermined pair of values is alike for all pairs of ports corresponding to similarly adjacent beams within said selected portion of said region.
 11. An antenna system as specified in claim 9 wherein said means for focusing incident wave energy comprises a cylindrical reflector.
 12. An antenna system as specified in claim 9 wherein said means for focusing incident wave energy comprises a focusing lens located between a pair of parallel conductive plates and wherein said feed elements comprise feed elements located between said pair of parallel plates.
 13. An antenna system as specified in claim 9 wherein the wave energy signals supplied to each of said ports have substantially equal amplitude thereby causing said antenna to radiate substantially equal amounts of radiation energy over said selected region of space and radiate smaller amounts of radiation energy in the remaining regions of space. 